Sergeant Keroro seems like a tough guy and can shoot some pretty powerful energy blasts. Of course Poliwrath can spam his various beams like Icebeam, Hyperbeam, and others. Poliwrath is also very strong physically and is durable. Poliwrath wins his first fight and rises up the blog ranks. Poliwrath wins.
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Poliwhirl also has access to evolving Politoed, giving him slight psychic capabilities, Drizzle and Perish Song. But even so, Keroro has access to some of Kururu’s inventions. Tough fight…
I actually forgot about some of Politoed’s abilities. They definitely help. Keroro is still a tough fighter, and his energy blasts helped, but I’m not sure if he could cope with Poliwrath’s random attacks. He could be using Earthquake while spitting out an ice beam. Of course he won’t want to waste attacks since it will drain his energy.